The invention relates to a closing edge safety device.
A closing edge safety device is described in FR 21 35 922 A1. In this arrangement, a tube consisting of soft material has arranged inside it balls which preferably consist of steel and have a diameter which is somewhat smaller than the inside diameter of the soft tube, the tube being elastically elongated while it is being filled with the balls. Still in this elongated state, the two openings of the tube are closed with plugs, to which the contact lines are connected. The plugs together with the tensioned tube produce within the tensioned tube the required pretension with which the balls abut one another.
If the balls are moved apart from one another by local deforming pressure, the current is interrupted and a signal is generated.
The known arrangement has not been adopted in practice, since the balls do not center themselves in the soft tube, but are instead displaced with respect to one another to move away from the pretension produced by the tube, so that a straight chain of balls is not obtained in the finally installed state. In this situation, the balls may deform the outer surface of the tube, so that there are difficulties when the tube is installed, but it may also be the case when the local deforming pressure occurs that the uncentered balls prevent the necessary signaling.
In WO/97 38 199 there is a description of a closing edge safety device in which an elastic contact element bed which is adapted to the shape of the contact elements and receives the contact elements individually in each case is fashioned in an elastic tube and is arranged fixedly with respect to the tube and on the side of the tube subjected to force, so that on the one hand the contact elements are mounted fixedly in the contact element bed and on the other hand the bending radius in the center axis of the chain of contacts formed by the contact elements is greater than the bending radius of the actual contact element bed. In this literature reference, it is also proposed that the contact elements may additionally have an expander cord passing through them.
This arrangement is complex, since the molding of the contact element beds of course requires expenditure on a mold and it must be ensured that the arrangement of the contact element beds and the size of the contact elements are adapted to one another in such a way that the contact elements touch one another in the state of rest.
The invention is based on the object of providing a closing edge safety device with which it is to be ensured that the contact elements used, preferably balls or ball-like parts, are correctly aligned, but nevertheless respond to the slightest deforming pressure by signaling. Furthermore, the production expenditure is, however, to be kept low.
While in the case of all safety strips of the prior art considerable amounts of expenditure are devoted to providing that the contact elements, no matter whether they are designed as balls, rollers or however else, are pressed against one another at their contact zones, it is now proposed according to the invention that the contacting of the individual contact elements with one another can take place merely by the force of gravity, i.e. by the weight of the contact elements, if the safety strip is vertically aligned. It goes without saying that the contacting of the elements with one another achieved in this way is all the better the heavier the elements, but in any event the elements are of a weight which is adequate for contact-making abutment with one another when the safety strip is perpendicularly installed.
According to one aspect of the invention, it is provided that the contact elements center, themselves within a tube, which can preferably be designed as a pliable tube, by being magnetized, that is to say lying with their opposing poles against one another, and holding one another firmly, thereby producing the required pretension with which the individual contact elements touch one another in the installed state.
According to another aspect, it is proposed that the chain of balls is designed as a closed structural system, which can move about in the tube as a closed unit, since the expander cord ensures the contact, so that as a result the tube can be adapted to any desired geometrical shape and even the tightest radii can be produced if the contact elements are of a correspondingly small design, so that in automotive engineering in particular, for example when providing fuse protection for the rubber closing strip on truck lids, an undesired displacement of the balls when laying in tight curves cannot occur. Instead of the expander cored, a wire spring arrangement or the like may also be used.
According to another aspect of the invention, the contact elements are designed as simple balls.
According to a preferred embodiment, the contact elements are designed according to the invention as part-spherical balls which have peripheral contact surfaces. As a result, improved contact forming is achieved; a greater touching surface area is ensured, so that lower resistance is brought about and the centering of the contact elements is better and easier.
Furthermore, it is provided according to the invention that the contact element may in this case be constructed by using a conductive sleeve, encapsulated by a sheath of plastic. In this case, the sleeve has plane-parallel surfaces.
It is also possible for each contact element to be of a part-spherical design and beveled shape, so that laying in a curve is more easily possible as a result. By appropriate choice of the beveling, it is possible to correspond directly to the curve radius.